Switched-mode power converters are used in a variety of electronic circuits and systems requiring conversion of a direct current (DC) input to a lower, or higher, DC output. For example, a switched-mode power converter may be implemented as a voltage converter, such as a buck converter, to convert a higher voltage DC input to a lower voltage DC output for use in low voltage applications in which relatively large output currents are required.
Switched-mode voltage converters typically include a current sense element or elements in series with one or more of the voltage converter power switches, as well as circuitry for monitoring the power switch current levels. This may be necessary to protect the power switch or switches from exposure to possibly damaging high peak currents. In a conventional solution for implementing current sensing, a low value ohmic resistor typically serves as the current sense element and is situated between the power switch and ground. However, power losses across such a conventional resistive current sense element can be large. In addition, system cost and size can increase significantly due to necessary additional components needed to implement a conventional resistive current sense element in applications in which very high currents are being switched and/or multiple sensing resistors requiring heat sinking are used.